step-by-step
\left(\left(\frac{x}{100}\cdot 2.04\right)+\left(\frac{100-x}{100}.1\right)\right)-\left(\left(\frac{x+8}{100}\cdot 1.94\right)+\left(\frac{100-\left(x+8\right)}{100}\cdot 1\right)\right)=0
vi